In a large pot, heat the caramelized onions and cooking liquid with the beef and chicken broth, the wine and pepper. Season to taste with the salt, if necessary.

When ready to serve, ladle hot soup into ovenproof serving bowls. Top each with 1 of the toasts (trimmed to fit inside of bowl) and sprinkle generously with some of the cheese. Place bowls on a baking sheet under oven broiler and broil just until cheese bubbles, melts and begins to turn golden. Serve immediately.